Number equal or larger than 100000000000000(1.0E+14) will represent by Scientific Notation(科学记数法), cause base_convert() loose precision. So for larger number, use BC Math or GMP. This array is used to check number string length per base, if string is longer than the array value, it should not use build-in base_convert(). Un-formatted for run usi…

compute-base-convert-safe-length.php

for ($j = 2; $j < 63; $j ++) {
$x = $j; $i = 1; $y = $x;
while ($y < 100000000000000) {
$i ++;
$y = pow($x, $i);
}
$i --;
$y = pow($x, $i);
echo "$x^$i = $y, length " . strlen($y) . "\n";
}